JPS6269220A - Aspherical zoom lens - Google Patents

Abstract

PURPOSE:To realize a large operate ratio and abberation compensation regardless of a small number of lens elements by composing a zoom lens of five groups and satisfying specific conditions. CONSTITUTION:A relay lens system has positive refracting power and consists of the 4th group composed of an aspherical single lens and the 5th group composed of an aspherical cemented lens which has positive refracting power and is provided at a relatively large interval with the 4th group, and conditions shown by inequalities are satisfied. In the inequalities, f4, f5, and fR are the focal lengths of the 4th, the 5th groups and relay lens, d15 the air gap between the 4th and the 5th groups, and nu4 the Abbe number of the single lens constituting the 4th group, nu5a and nu5b the Abbe numbers of the negative and positive lenses of the cemented lens of the 5th group. Further, the 4th and the 5th groups each have at least one aspherical surface shape.

Description

[Detailed Description of the Invention] Industrial Field of Application The present invention relates to a zoom lens for a video camera, and in particular, provides a high-performance zoom lens that reduces the number of lenses by utilizing an aspherical surface, and is compact and lightweight. It is something to do.

Conventional technology In recent years, emphasis has been placed on operability and maneuverability in video cameras, and in response to this demand, imaging devices have also become 1.2 ym (14 mm).
Small size (inches) is becoming mainstream. In addition, there is a strong demand for high-performance zoom lenses that have a large aperture ratio, a large zoom ratio, and are compact and lightweight. Furthermore, there is a strong desire to reduce costs, and there is a strong need to realize a zoom lens that reduces the number of lenses while maintaining high performance.

Conventional zoom lenses have an F number of 1.4. (The -me ratio is about 6, and each group constituting the variable magnification section has 3 focusing sections, 3 variators, 1 compensator,
Many have a configuration of 6 to 8 relay lenses. In the case of a video zoom lens, the exit pupil position must be at least a certain distance from the image plane to prevent color shooting.
Since the crystal plate is placed in front of the imaging surface, there is a constraint that a long back focal length is required, and in order to realize a high-performance zoom lens, a relay lens consisting of a large number of 6 to 8 spherical lenses is essential. there were.

The problem that the invention aims to solve However, in the above configuration, the shape is spherical.

Even with optimal design such as 2-spherical lens arrangement, there are limits to the design, and while maintaining the aperture ratio, zoom ratio, and imaging performance,
It is difficult to reduce the number of constituent sheets.

The present invention takes advantage of the aspherical shape and has an F number of 1.4 despite the unprecedentedly small number of 10 elements.
．． The present invention provides a compact and high-performance zoom 1/lens for video cameras with a zoom ratio of 6.

Means for Solving the Problems The configuration of the aspherical zoom lens of the present invention is as follows from the object side:
A first group as a focusing section with positive refractive power, a second group as a variator section that has negative refractive power and changes magnification by moving on the optical axis, and an image that changes as the variator section moves. The third group serves as a compensator section that keeps the plane at a constant position from the reference plane, and the first group. Second. The relay lens system connects to the transformation system formed by the third group, and the relay lens system has a positive refractive power and a fourth group consisting of an aspherical single lens; The lens is composed of a fifth group consisting of an aspherical cemented lens having positive refractive power and spaced apart from each other with a relatively large air gap, and satisfies the following conditions.

0) t, o(8/fR(1,5 @1.2<f5/IR<2.7 (3) 0.4 <d15/f!I<0.7 (4)
ν4〉66 (6) shi, b-shisa) 2 g (e) The fourth group and the fifth group each have an aspherical shape of at least one stroke. However, f4. 8r fH is the focal length of the fourth group, the fifth group, and the relay lens, d, 5 is the air distance between the fourth group and the fifth group, ν4 is the Atsube number of the single lens constituting the fourth group, C51. h and b indicate the Abbe numbers of the negative lens and positive lens forming the cemented lens of the fifth group.

Effect The present invention has the above-described configuration, that is, by utilizing the aspherical shape and selecting an appropriate lens type and lens material,
Despite having an unprecedentedly small number of lenses, it has achieved a large aperture ratio and excellent aberration correction.

EXAMPLE An example of the present invention will be described below with reference to the drawings.

FIG. 1 shows a configuration diagram of an embodiment of an aspherical zoom lens according to the present invention. In FIG. 1, 1 is the first group;
2 is the second group, 3 is the third group, 4 is the fourth group, 6 is the fifth group, 6
is an equivalent glass plate corresponding to a crystal filter or a 7-eighth plate of an imaging device.

The above condition (1) is a condition regarding the power of the fourth group which is a part of the relay lens system. If the lower limit is exceeded, the power of the single lens becomes too large, making it difficult to correct spherical aberration, and creating an aspherical shape with a large deviation from the spherical surface, which causes problems in manufacturing the lens. If the upper limit is exceeded, the degree of divergence of the light beam exiting the fourth group 4 will increase, and the height of the ray of light in the fifth group 5 will increase, so the lens diameter will be too large.

Condition @) is a condition that defines the power of the fifth group.

If the lower limit is exceeded, the power of the negative lens and positive lens forming the cemented lens of the fifth group 5 will be too weak, making it difficult to correct aberrations. If the upper limit is exceeded, the back focus will be shortened and the necessary exit pupil position will not be secured.

Condition (3) is the air gap d4 between the fourth group 4 and the fifth group 6.
．． This stipulates the following. If the lower limit is exceeded, astigmatism becomes too negative, making it difficult to correct field curvature. If the upper limit is exceeded, the height of the upper ray of the off-axis beam becomes high, making it difficult to correct aberrations, and making it impossible to realize a compact lens with a long lens length.

Conditions (4) and (5) relate to correction of chromatic aberration. Condition (4) defines the Abbe number of the positive lens in the fourth group 4, and condition (5) defines the difference in Abbe number between the positive lens and the negative lens constituting the cemented lens in the fifth group 6.

Outside the range of condition (4), it is difficult to correct Hosochi chromatic aberration, and outside the range of condition (6), it is not possible to satisfactorily correct chromatic aberration of magnification.

Is the condition (6) that the fourth group 4 and the fifth group 6 each have at least one stroke of aspherical shape possible under an extremely small number of constituent elements? This lens is indispensable for correcting aperture aberrations and off-axis aberrations with a large aperture number of 1.4. By arranging the aspheric surfaces with large air gaps, aberration correction is performed very effectively.

The diaphragm is placed immediately before or after the fourth group 4.

Therefore, the fourth group 4 is the position where the light beam becomes the thickest in the relay lens system, and the aspheric surface in the fourth group is effective for correcting aperture aberration. However, this is not enough and the fifth
This works in combination with the aspherical surface of the group. The fifth group corresponds to a portion of the relay lens system where the height of off-axis rays becomes high, so it is effective in correcting off-axis aberrations.

Under the lens configuration and conditions according to the present invention, the y-number is approximately 1.4. We were able to create a compact, high-performance video camera zoom lens with a zoom ratio of approximately 6x, consisting of 10 elements.

Examples that meet these conditions are shown below. “1+” in the table
r2... is the radius of curvature of each lens surface counted from the object side to the head, d15d2... is the wall thickness or air gap between lens surfaces, "+t"2...・ is the refractive index of each lens for the d-line; C2...is d
This is the Atsbe number for the line. In addition, surfaces with aspherical shapes (displayed in the headquarters) are defined by the following display.

However, 2: Distance from the tangent plane of the aspherical vertex of a point on the aspherical surface with height y from the optical axis: y: Height from the optical axis C: Curvature of the aspherical vertex (=1/r) , D, IC, F, G: Aspheric coefficient (Example 1) f=8.842 to 49.511 F=1:1.4
4*r,=143.424 dl=158Q n1=
1.58407 v, = 3o, x* r2 = 25.254 a2 = 2.38 ner5 = 36.948 d3: 8.10 n2 =
1.49178 1/2==57.2* r4 =-146,952 (14= 0.20r5=
31.555 d5=g, 4Q n3=1.58
913 173=61.2r6 =-251,189(
16 (variable) r7 = 66.343 4!7 =
0.90 n4 = 1.69100 ν4 =
54.8r6 = 12.243 <16 = 4
．． 74rp = -14,859 (!9: 1.00
n5 = 1.69100 95 = 54.8 + 1g
: 30.915 (!1Q=2.64 n6=
1.80518 ν4=25.5 rate r15= -56,910411 (variable) r12==
-21,376a12=o,son7=1.516
33 Schiff: (i4, 1r13= -sα108
(!ts (variable) r14 = 22.144 a14
=tto n6=1.62280 176=56.9
r, := −33,470 (!15=10.20r, 4
: 30.808 dt6= 1.00 n9=
1.80518 179 = 25.5r11=
10.509 (117=7.2OnIQ=1.
62280 ν+o = 56.9* r18= -28,689 (1, $= 1.00r1?
:: O) d1p= 5.40 n
11= 1.51633 J/11::64.1r2
0=ω Note that the surface marked with * is an aspherical surface and is expressed by the following constant.

1st side 2nd side 3rd side -9,51190X1G -1,80958X10
2.21605X10'D-9,88346X10
-7-2.83319X10-61.76836X10
″Expletive 2.23281X10 -1.23071X1
0 -7.71183X10''F 1.6794
3 X 10 -9.30155 X 10 8
．． 88904X 10.12G 1.56848X
10-15-2.15930X10-14-1.616
27X10” 4th side 11th side 16th side K -8,80180X 10° -3,90910X
10-' Q, OD 4.23380X10'-
1,73009X10-55.15746XI0.5X
2.30931X10=' 2.05080X1
0-7-2.77019X1 (1-8F 4.386
71X10-12-2.42754X10=1.3
5008X10"G 5.57443X10-1'
1.03228X10-”-9,94787X10
``''15 18th surface ICO□OD D 8.40309 X 1G= x4.27549 shown.

! (!16 d11a1s8.84
2 1.50G4 28.7438 3
．． 000124.222 19.1660
6.4141 7.664249.51!
26.6342 3.6133 2.9
968f4/9=1.20. f5/fR-1, a3.
dis/9 - 0,55° 4 = 56.9. C5b
-Si4>55ν5b-ν5a, = 31.4 (Example 2) f=a, s4o ~49.502 F=1:1.44
(The 1st group, 2nd group, 3rd group, and 5th group are common to Example 1.) j14:: 23.229 d14= 4.80 n
6==1.51633 J/6:541*r, 5=-36,717d15=tz,o.

r16= 21.012416=1.00 nq=
1.80518! '? :215r17=11.
089 d17=s,oo nIQ=1.5891
3 SijQ=61.2r, :=-32,048(!1
8: 1.00 16th page 18th page K o, o o,
.

D 4.18412X10, 1.51023
X10-51! 6.35155 X 10-9-
7.38446 X 10″″8F1.00488 X
10” 5.98791 x 10″″″.

G -1,15261X10" -6,96463
X10'-12! a/fH="42- fy'fH="
”, dt5/11=α60°shi4=64.1.
5b-5a=35.7 (Example 3) f=s, ssa ~49.490 F=1:1.4
4 (1st, 2nd, 3rd, and 5th groups are the same as in Example 1) r1
4= 1&338 (114= 5.80 nq
= 1.62041 1/6 == tso, 3 r15=-28,122 (!15=8.50r16=
81.310 a14=too n9=1.80
518 shi9=25.5r17=12.590
1117=[Q n1Q:1.62041, ν1
(1:5Q, 3X%:= -23,156111$ =
1.00 Page 16 Page 18 K o, o o,.

D 8.24593 X 10-53.74191
X 10-'Expletive-9.29928X10-84.80
317X10-7F 2.43766X10='
-4,19920X10=G-1,44449X10
=25.90082X10='f4/fR=1.07.
f, /fR=2.54. d1. /fR=0.48゜1/
4=d5Q, 3.115b-ν51L=34.8 (Example 4) f=a, s4o ~49.502 F=1:1.4
4 (1st, 2nd, 3rd, and 5th groups are the same as in Example 1) r1
4= 22.180 414= 4.90 nq=
1.65160 3115 = 58.5* r15 = -33,361d15 = 9.50r1
6: 31.133 +116=1. oo np
=1.80518 shi51:25.5r17==
9.740 (117:7.40 1111) = 1
．． 61484 νjQ=51.1ner197−-27.575 (11B=1.00 1st
5th side K o, o o,.

D5.22990 x 10=-7,36226
X 10'X-3.20278X10-82.230
66X10"7 1.37780 X 10"
-4,29517X 10.10G -8,2230
3X10"-9,06673X10=2f4/f,
=1.17. f5/8=1.98. d4>55ν5
b-ν5a/7. =0.52°ν4=58.5. Heb-
C5. =25.8 (Example 6) f=a, a+o ~49.502 F=1:1.4
4 (1st, 2nd, 3rd, and 5th groups are the same as in Example 1) r1
4=21.950 (1j4=5.10 nq
=1.60311 1/6=5Q, 7ne rj5=-31,419d15=10.70 pieces r16= 30.822 a16= 1.00
n9 = 1.80518 1/? =25.5rj7=
11.319 (!i7= 6.90 n1Q
== 1.60311 si1g=6o, 7r19=-
26.999 a1B=to.

Page 15 Page 16 x o, o, o.

D 5.37911 X 10' -2,93
787X 10'E -3,25065X 10
' -4,74602X 10"F 1.249
33X10"9.51165X10"G -7
,68690X 10 -4.32526X 10
=3f4/8-1,19,f,/to=1.79. d1
5/71% ==Q, 57° 4; θo, 7. C5b-
C5. =35.2 2nd. Third. Figure 4 is a wide-angle view of Example 1.

Shows aberration performance at standard and telephoto. Similarly, the fifth, fifth . FIG. 7 shows the 8th, 9th and 9th sections of Example 2, respectively. 10th
The figure shows the 11th example of Example 3. 12゜Figure 13 is Example 4
14th. 16th. FIG. 16 shows the aberration performance of Example 6 at wide angle, standard, and telephoto, respectively. From the figure, it can be seen that each example has good optical performance.

Effects of the Invention As is clear from the above explanation, under the lens configuration and conditions of the present invention, the number of lenses is as small as 10. The number is about 1.4. A compact and high-performance zoom lens with a zoom ratio of approximately 6x has been realized.

[Brief explanation of drawings]

Fig. 1 is a configuration diagram of an aspherical zoom lens according to an embodiment of the present invention, Figs. 2, 3, and 4 are various aberration diagrams of embodiment 1, and Figs. 5, 5, and 7. are various aberration diagrams of Example 2, Figures 8, 9, and 10 are various aberration diagrams of Example 3, and Figure 11 is a diagram of various aberrations of Example 2.
12, 13 are various aberration diagrams of Example 4, and 14.
15 and 16 show various aberration diagrams of Example 6. In the diagram of spherical aberration, the solid line shows the spherical aberration with respect to the d-line, and the dashed-dotted line shows the spherical aberration with respect to the C-line. In the diagram of astigmatism, the solid line shows the sagittal curvature of field, and the 9-dot line shows the meridional curvature of field. 1...First group, 2...Second group, 3...
...3rd group, 4...4th group, 6...
・Fifth group, 6...Crystal filter. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 23
) FIG.
"E(-) 4 m bite("L(%) 5th rl
! J 蕉i 电C にりい〜燵(-distortion 14(庭Fig. 5Fig. 7-ati-ax-aza, aa, t-t, aaas.gf#ゆ('LD'=) 114.aJ (-a
) 11h u('i') Figure 8 Figure 9'' Rumor (Uri No. NU; Shisame 'tr% ri) End A1, 噌car 11 Supplementary; 1E (C) Figure 10, J≧ 4%
, stand, lj (, 4th, (-1 n j solid lie hawk; difference (L) Fig. 11 O] t ts difference (%, ) 4#LOi (-l distortion tolerance 1 hawk) Figure 12 Figure 13
j Hirulinu A (-4n Fig. 14 Fig. 15 1μm to 2-unseen (edge positive 6pi (spring 2 Fig. 16 -az (1,0az MmtJL,! (-ri)

Claims (1)

[Claims] In order from the object side, a first group as a focusing section having a positive refractive power, and a second group as a variator section having a negative refractive power and changing magnification by moving on the optical axis. a relay lens connected to the variable magnification system formed by the first, second, and third groups; The relay lens system has a positive refractive power and a fourth group consisting of an aspherical single lens, and a fourth group provided at a relatively large air distance from the fourth group. An aspherical zoom lens comprising a fifth group consisting of an aspherical cemented lens having a positive refractive power and satisfying the following conditions. 1.0<f_4/f_R<1.5 1.2<f_5/f_R<2.7 0.4<d_1_5/f_R<0.7 ν_4>55 ν_5_b−ν_5_a>25 The fourth and fifth groups are respectively It must have an aspherical shape with at least one stroke. However, f_4, f_5, f_R are the focal lengths of the fourth group, the fifth group, and the relay lens, respectively, and d_1_5 is the focal length of the fourth group.
The air distance between the groups and the fifth group, ν_4, is the Abbe number of the single lens constituting the fourth group, and ν_5_a, v_5_b are the Abbe numbers of the negative lens and positive lens forming the cemented lens of the fifth group.